Pennsylvania Turnpike tolls are scheduled to go up 6 percent early next month in what will mark the 10th straight year of rate increases along the nation's oldest superhighway.

Toll hikes used to be uncommon. In the 67 years before 2009, tolls went up just five times - in 1969, 1978, 1987, 1991 and 2004. The toll most commonly paid by drivers of passenger vehicles, or generally the amount that it costs to travel from one turnpike exit to the next, stood at 75 cents in 2008, according to the Turnpike Commission.

When the next round of toll hikes take effect Jan. 7, the commission said the most common toll shelled out by cash-paying customers will be $2.10 - nearly triple what it was a decade earlier. The average toll for E-ZPass customers will be $1.30 - a 73 percent jump from 2008.

The Turnpike Commission said it needs to impose annual toll hikes so it can make annual payments to PennDOT and pay for improvements to its own 550-mile network of highways.

“The Turnpike Commission is obligated by state law to augment Pennsylvania's infrastructure needs . At the same time, we must also continue to invest in our aging tollway system and make it safer, wider and smoother for our customers,” Turnpike CEO Mark Compton said in a news release.

Turnpike spokesman Carl DeFebo said the commission has provided nearly $6 billion to PennDOT since August 2007 to help pay for road and bridge projects and to support public transit systems across the state. Its last payment in October totaled $112.5 million. The commission has also rebuilt about 124 miles of its own highway system, and is currently improving and widening another 20 miles and is preparing to begin work on another 90 miles.